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Published online before print November 22, 2005, 10.1148/radiol.2381041532
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(Radiology 2005;238:280-291.)
© RSNA, 2005

Technical Developments

Atherosclerotic Disease: Whole-Body Cardiovascular Imaging with MR System with 32 Receiver Channels and Total-Body Surface Coil Technology—Initial Clinical Results1

Michael Fenchel, MD, Albertus M. Scheule, MD, Norbert I. Stauder, MD, Ulrich Kramer, MD, Katrin Tomaschko, RT, Thomas Nägele, MD, Christiane Bretschneider, Heinz-Peter Schlemmer, MD, Claus D. Claussen, MD and Stephan Miller, MD

1 From the Departments of Diagnostic Radiology (M.F., N.I.S., U.K., K.T., C.B., H.P.S., C.D.C., S.M.), Cardiovascular Surgery (A.M.S.), and Neuroradiology (T.N.), Eberhard-Karls-University, Hoppe-Seyler-Strasse 3, 72076 Tuebingen, Germany. Received September 10, 2004; revision requested November 18; revision received January 20, 2005; final version accepted February 21. Address correspondence to M.F. (e-mail: michael.fenchel{at}med.uni-tuebingen.de).


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 References
 
In this prospective study, the feasibility of a comprehensive cardiovascular imaging protocol with a dedicated whole-body 1.5-T magnetic resonance (MR) imager with 32 receiver channels in 34 patients with peripheral arterial occlusive disease was evaluated. Informed consent and institutional review board approval were obtained. Three-dimensional MR angiographic data sets were acquired with adapted injection protocol. Cardiac functional imaging and delayed-enhancement imaging were performed, as were fluid-attenuated inversion-recovery imaging of the brain and time-of-flight MR angiography of the intracranial blood vessels. Sensitivity and specificity for depiction of significant vascular stenosis (> 70%) were 96%, with conventional digital subtraction angiography as the standard. Substantial microangiopathic tissue alterations (n = 4) and/or cerebral infarction (n = 4) were diagnosed in seven patients. In seven patients, subendocardial or transmural delayed enhancement was detected in corresponding regions, indicating prior myocardial infarction. Previously unknown findings diagnosed with MR imaging required midterm follow-up or therapy in 24 patients, whereas change of therapy or immediate treatment was necessary in three. For patients suspected of having systemic atherosclerotic disease, comprehensive risk assessment is feasible within 30 minutes.

© RSNA, 2005


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 References
 
Atherosclerosis constitutes a serious health burden in developed countries. With its ever-increasing rate of occurrence, this disease is about to emerge as a principal cause of worldwide morbidity and mortality (1). Treatment strategies that include surgical and percutaneous catheter-based interventions, as well as pharmacologic treatment, require an accurate assessment of atherosclerotic manifestations with respect to location, extent, and severity of arterial involvement (2,3). At the present time, several imaging techniques that include conventional angiography, duplex ultrasonography, computed tomographic angiography, and magnetic resonance (MR) angiography are being used for this purpose in clinical practice. Despite general agreement that atherosclerotic disease is systemic in nature and that it influences the entire macro- and microvascular system (4,5), the diagnostic approach to atherosclerosis has remained locally focused on the symptomatic clinical problem. This is mainly because of limitations that are inherent in the selected imaging techniques. Risks associated with invasive procedures and contrast agent dose and radiation dose limitations, as well as monetary and time constraints, have led to a diagnostic analysis that was focused on one arterial region.

It is generally recognized that local assessment of the vasculature by using MR angiography provides a high diagnostic standard for depiction of the most relevant territories of atherosclerotic predilection (ie, the brain, heart, kidney, and arterial vascular tree). First attempts have been made to accommodate the systemic nature of atherosclerosis by introducing whole-body MR angiography (6) or whole-body screening protocols (7–10) to clinical use. These techniques, however, come along with compromises in regard to acquisition of adapted sequence conditions or spatial resolution, as well as total body coverage. Furthermore, a comprehensive examination for atherosclerotic disease needs the capability to depict postischemic lesions in the brain and the heart, and this capability has not been addressed in most previous studies.

Recently, a 1.5-T whole-body MR imaging system equipped with 32 independent receiver channels has been introduced. The 32 receiver channels allow simultaneous acquisition of high-spatial-resolution data from as many as 32 phased-array surface coils within the field of view. The coil technology enables parallel imaging in multiple spatial directions to accelerate image acquisition. This is particularly important for whole-body bolus-chase techniques, inasmuch as imaging time for each body region is restricted by the traveling speed of the bolus of contrast agent. Researchers in only a few previous studies have performed whole-body MR angiography (6,11–13) in which parallel data acquisition was used (14). In those studies, however, signal reception with the body coil, repositioning of surface coils, or an approach with a sliding table were necessary.

Thus, the aim of the our study was to prospectively evaluate the feasibility of a comprehensive cardiovascular imaging protocol implemented with a dedicated whole-body MR imager in patients who have atherosclerotic disease.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 References
 
Subjects
Thirty-four consecutive patients (22 men, 12 women; mean age, 64.91 years ± 12.55 [standard deviation]; range, 34–84 years) who met our criteria and were referred for conventional digital subtraction angiography (DSA) from January 2004 to July 2004 were enrolled in the study. All patients had clinical evidence of peripheral arterial occlusive disease (PAOD). Furthermore, inclusion of patients was based on their ability and willingness to participate in the study, as well as their lack of contraindications to MR imaging. Informed consent was obtained from all participants in this study, and the study received approval of our institutional review board.

MR Imaging Protocol
All examinations were performed with a 1.5-T MR imager with surface coil technology (Magnetom Avanto; Siemens Medical Systems, Erlangen, Germany), which provided a gradient strength of 40 mT/m and a maximum slew rate of 200 mT/m/msec. For signal reception, surface coils were used for all body regions. Four or five overlapping fields of view of 500 mm were used, depending on the size of the subject. Individuals who were shorter than 180 cm in height were examined by using the four-station protocol. Overlap between adjacent fields of view was at least 40 mm so that the total coverage in the feet-head direction was 1800 mm for four fields of view and 2020 mm for five fields of view.

Individuals were placed in the supine position, and five phased-array surface coils were placed to the head (12 coil elements), neck (four coil elements), abdomen (six coil elements), pelvis (six coil elements), and lower extremities (16 coil elements). The spine coil, with 24 elements, is embedded in the patient table.

Prior to the examination, an 18-gauge intravenous catheter was placed into an antecubital vein of the right arm to facilitate contrast medium injection. Scout images were obtained from all stations, and these images included a low-resolution phase-contrast scout image of blood vessels (repetition time msec/echo time msec, 31/11; matrix, 56 x 256; field of view, 219 x 500 mm; flip angle, 10°; bandwidth, 190 Hz/pixel).

The examination protocol comprises the acquisition of images of the patient's brain, heart, and arterial vascular system. Detailed parameters for imaging sequences are provided in Table 1.


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  		Table 1. Parameters for Imaging Sequences

 
First, cerebral imaging was performed with a FLAIR sequence to detect chronic intracranial lesions and cerebral infarction (15–17). Subsequently, cardiac cine images, which covered the three major cardiac axes, were obtained. A cine true fast imaging with steady-state precession retrogating sequence was used for imaging in the four-chamber view and the perpendicular long-axis view, whereas a cine true fast imaging with steady-state precession sequence with phase sharing (temporal resolution, 39.8 msec) was used for imaging in the short-axis view. Circulation time was determined by using 2 mL of gadopentetate dimeglumine (Magnevist; Schering, Berlin, Germany), with a sagittal section angled to the course of the aorta. Intracranial arteries were examined by using a multislab 3D time-of-flight angiographic sequence, with use of a tilted optimized nonsaturation excitation pulse for each slab (18). To maximize the vessel-to-background contrast, time-of-flight images were acquired after the administration of the test bolus (2 mL of gadopentetate dimeglumine). A total of 0.25 mmol per kilogram body weight gadopentetate dimeglumine was administered for all contrast material–enhanced MR angiographic studies.

Unenhanced images were acquired from stations 2–4 or 5 by using a 3D FLASH sequence that was optimized for high spatial resolution and short acquisition times. For stations 2–4 or 5 (ie, thoracic, abdominal, and peripheral arteries), the imaging delay was calculated according to the following formula: Tcir(aor/ren) – Tk + 4 sec, where Tcir(aor/ren) is the circulation time at the level of the ascending aorta (station 1) or the renal arteries (stations 2–4) and Tk is the time to the k-space center line. In all individuals, 0.15 mmol/kg contrast medium was injected at a rate of 2 mL/sec, followed by injection of 0.03 mmol/kg contrast medium at a rate of 1 mL/sec. After injection of contrast medium, tubing and veins were flushed with 25 mL saline at a rate of 1 mL/sec.

Subsequently, unenhanced images from station 1 (supraaortic vessels, intracranial vessels) were acquired. For station 1, the circulation time was measured in the ascending aorta, and the imaging delay was calculated as described previously. Contrast-enhanced images of station 1 were acquired after injection of 0.07 mmol/kg contrast medium at a rate of 2 mL/sec, followed by injection of 10 mL saline at a rate of 2 mL/sec and of 25 mL saline at a rate of 1 mL/sec. For stations 1 and 2, patients were asked to hold their breath in expiration to acquire imaging data free of breathing artifacts. Baseline images were subtracted from the contrast-enhanced images for each station to remove background signal and increase the vessel-to-background contrast.

Finally, 10 minutes after contrast medium injection, an inversion-recovery turbo FLASH sequence was used for acquisition of delayed-enhancement images in the three main cardiac axes. By using a dedicated inversion time scout sequence (2.6/1.12; matrix, 78 x 192; field of view, 276 x 340 mm; section thickness, 8 mm; flip angle, 50°; bandwidth, 965 Hz/pixel), the inversion time was chosen to minimize the signal from normal myocardium.

Total imaging time was 29 minutes in all individuals. Total in-room time was 50–55 minutes.

Conventional DSA
DSA of the symptomatic region of the patient (usually comprising the distal aorta, the renal and pelvic arteries, and the arteries of the lower extremities) was performed by an experienced radiologist who had 8 years of experience in diagnostic and interventional angiographic procedures with a standard angiographic unit (Axiom Artis TA; Siemens Medical Systems). A 4-F straight catheter was inserted transfemorally, and 20 mL of contrast material (Ultravist 370; Schering) was administered at each station (total of 160–200 mL of contrast agent). As required, examinations were supplemented with acquisition of one or more oblique views of the arteries or with selective catheterization of individual extremities. Selective injections were not routinely performed.

Image Evaluation of MR Angiographic and DSA Images
Postprocessing for generation of maximum intensity projection reconstruction images required about 5 minutes. All MR angiographic images were prospectively interpreted by one radiologist (U.K.) who had 5 years of experience in cardiovascular MR imaging and was blinded to the results of DSA and the medical history of the patient. Maximum intensity projection reconstruction was performed for each station. Maximum intensity projection reconstructions and contrast-enhanced source images were used for image analysis on a segment-by-segment basis for review.

DSA images were evaluated by another board-certified radiologist (N.I.S.) who had 6 years of experience in cardiovascular MR imaging and in diagnostic and interventional angiographic procedures and was unaware of MR imaging findings. MR angiographic and DSA images were interpreted with regard to arterial stenoses and other vascular disease. DSA was used as the standard of reference.

For image evaluation, the vascular system was classified into the following segments: segment 1, left and right intracranial carotid arteries; segment 2, left and right anterior cerebral arteries; segment 3, left and right medial cerebral arteries; segment 4, left and right posterior cerebral arteries; segment 5, basilar artery; segment 6, left and right internal carotid arteries; segment 7, left and right common carotid arteries; segment 8, left and right vertebral arteries; segment 9, left and right subclavian arteries and brachiocephalic trunk; segment 10, thoracic aorta; segment 11, suprarenal abdominal aorta; segment 12, infrarenal abdominal aorta; segment 13, left and right renal arteries; segment 14, left and right common iliac arteries; segment 15, left and right external iliac arteries; segment 16, left and right common femoral arteries; segments 17 and 18, left and right superficial femoral arteries divided into proximal and distal halves; segment 19, left and right popliteal arteries; segment 20, left and right tibioperoneal trunks; segment 21, left and right anterior tibial arteries; segment 22, left and right peroneal arteries; and segment 23, left and right posterior tibial arteries. Therefore, a total of 42 arterial segments were assessed.

Image quality of MR angiographic data sets was rated according to characterization of each arterial segment by using a five-level scoring system modified from that of Danias et al (19). The scoring system follows: score 0, information was of poor quality (nondiagnostic); score 1, structures were visible but with substantial blurring and/or artifacts (diagnosis was suspected but not established); score 2, anatomy was visible with moderate blurring and/or artifacts (diagnosis could be established); score 3, minimal blurring and/or artifacts (diagnostic information of good quality, with definite diagnosis); and score 4, sharply defined borders (diagnostic information of excellent quality).

MR angiographic images and DSA images were interpreted for the presence of vascular disease by using the same segmental classification. Each vascular segment was assessed for the presence of stenoses with luminal narrowing of 30%–70% (not hemodynamically significant) and of 70%–99% (hemodynamically significant). Furthermore, vessel occlusion was recorded. MR angiography and DSA were compared for segments for which data from both modalities were available.

FLAIR images of the brain were assessed by one board-certified neuroradiologist (T.N.) who had 10 years of experience in brain MR imaging in regard to the presence of postischemic lesions and/or chronic cerebral infarction or other disease (eg, cerebral tumor).

Evaluation of cardiac images was conducted by one radiologist (U.K.) who had 5 years of experience in cardiovascular MR imaging. Cardiac left ventricular ejection fraction was calculated from serial short-axis sections by using dedicated software (Argus, version 2002B; Siemens Medical Systems). Furthermore, cine images were assessed for the presence of regional wall motion abnormalities. Severity (hypokinetic, akinetic, dyskinetic) and location of wall motion abnormalities were recorded. Contrast-enhanced inversion-recovery turbo FLASH delayed-enhancement images were assessed for the presence of myocardial infarction. Severity, transmurality (subendocardial, transmural), and location of delayed enhancement were recorded.

Findings in MR imaging examinations were compared with the patient's medical history and the patient's chart (M.F.). Previously unknown findings were recorded. Furthermore, those findings that required follow-up and findings that necessitated immediate therapy were also recorded.

Statistical Analysis
Continuous data are presented as the mean ± standard deviation. A difference with a P value of .05 or less was considered significant. Sensitivity and specificity for at least 70% or 100% stenosis (occlusion) was estimated by using generalized estimating equations, assuming that all measurements in the same person were correlated exchangeably (Stata 8.0; Stata, College Station, Tex). Another way to set the percentages of regions on a percentage-of-patients footing is to weight findings according to the reciprocal value of the number of truly affected or stenosis-free regions in that patient.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 References
 
Missing Data
The MR angiographic examination with the whole-body coil configuration was tolerated well by 29 of 34 patients. Mild claustrophobia in two patients was remedied with administration of 1 mg of lorazepam (Tavor; Wyeth, Collegeville, Pa) prior to the examination; however, two patients aborted the examination because of severe claustrophobia. In one patient, MR angiography of station 1, as well as time-of-flight and FLAIR imaging, could not be performed because of intolerance to the head coil. In this patient, only MR angiography of stations 2–4 and cardiac imaging were performed. Therefore, 32 patients were included in our evaluation, 31 with complete imaging studies and one with partial imaging studies.

MR Angiography and DSA
In MR angiographic examinations, a total of 1321 vascular segments were evaluated for the presence of vascular disease and image quality. The mean rating of MR angiographic image quality, with a five-point scale (score of 0–4), was 3.78 ± 0.55.

In six patients, venous superimposition hampered the diagnostic assessment of 23 (1.7%) of 1321 arterial segments, and multiplanar reconstruction of the contrast-enhanced data sets was required. Specifically, arterial evaluation was complicated by venous enhancement in the internal carotid artery (n = 5), the common carotid artery (n = 1), and the vertebral artery (n = 5), as well as in the tibioperoneal trunk (n = 3), the anterior tibial artery (n = 2), the posterior tibial artery (n = 5), and the peroneal artery (n = 2).

All anatomic variants evident on MR angiographic images were also confirmed with DSA examinations. In nine patients, a total of 15 additional renal arteries were detected with both modalities. Five patients exhibited abnormal branching of the anterior tibial artery (n = 3) and/or the posterior tibial artery (n = 3).

In regard to DSA, 628 vascular segments were evaluated in 32 patients, with abnormalities present in 245 segments (Table 2). Whole-body 3D MR angiography depicted 251 stenotic lesions or aneurysmal widening in these vessel segments, as well as 76 abnormalities in vessel segments that were not imaged with DSA (Table 3).


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  		Table 2. Results of Assessment for Abdominal and Peripheral Vascular Occlusive Disease

 

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  		Table 3. Results of Assessment for Supraaortal Vascular Occlusive Disease

 
Stenoses
Diagnosis of relevant and total stenosis with MR angiography resulted in six of 143 (total stenoses, two of 85) false-negative regions and in 19 of 485 (total stenoses, eight of 543) false-positive regions. The {kappa} value for agreement between MR angiography and DSA was 0.89 (total, 0.93). Naive estimates of sensitivity and specificity for depiction of at least a 70% (total, 100%) stenosis were 96% (total, 98%) and 96% (total, 99%) in regions, respectively, while generalized estimating equations estimates yielded a sensitivity of 96% (total, 98%) and a specificity of 96% (total, 98%). Weighting resulted in a sensitivity of 96% (total, 97%) and a specificity of 96% (total, 98%) in patients. Aneurysmal changes were correctly diagnosed in 13 vascular segments (suprarenal aorta, one segment; infrarenal aorta, eight segments; common iliac artery, four segments).

Concomitant Vascular Disease
In the present study, 18 (56%) of 32 patients with PAOD also exhibited evidence of high-grade cerebrovascular disease (>70% luminal narrowing), whereas hemodynamically relevant luminal narrowing of renal arteries (>70% luminal narrowing) was diagnosed in six (19%) patients. Coronary artery disease, as evidenced by wall motion abnormalities or delayed enhancement, was diagnosed in 22 (69%) patients.

MR Imaging of the Brain
Substantial microangiopathic tissue alterations (n = 4) and/or cerebral infarction (n = 4) were diagnosed in seven (22%) of 32 patients. In addition, 17 (53%) patients showed discrete microangiopathic lesions.

Three patients exhibited considerable cerebral encephalopathic changes (n = 2) or atrophy of cerebellar structures (n = 1). In one patient, assessment of cranial structures revealed an additional diagnosis of inflammatory alterations of the sinuses.

MR Imaging of the Heart
Mean ejection fraction of all our patients was 56.6% ± 11.6. At presentation, 21 (66%) of 32 patients had hypokinetic and/or akinetic (n = 16) or dyskinetic (n = 6) myocardial regions. Diastolic relaxation abnormalities were diagnosed in two patients. In seven patients, these regions also displayed subendocardial or transmural delayed enhancement, which indicated prior myocardial infarction. One patient exhibited a left ventricular aneurysm secondary to myocardial infarction. Subjects with wall motion abnormalities exhibited a mean ejection fraction of 50.9% ± 7.3. Furthermore, myocardial hypertrophy was evident in two patients, whereas valvular disease was observed in three patients (mitral valve prolapse, n = 1; mitral valve thickening, n = 1; tricuspid insufficiency, n = 1). Left ventricular thrombus formation was detected in one patient.

In regard to delayed-enhancement images, one patient exhibited a disseminated and patchy accumulation of contrast agent in the left ventricular myocardium, which was probably caused by systemic or inflammatory disease.

Previously Unknown Findings
Previously unknown vascular findings were evident in 27 (84%) of 32 patients. Furthermore, cerebral imaging revealed new findings in five (16%) patients, whereas assessment of cardiac structures and function yielded new disease in 14 (44%) patients.

Overall, these findings required midterm follow-up or therapy in 24 (75%) of 32 patients, whereas in three (9%) patients, a change of therapy or immediate treatment was necessary (bilateral aneurysm of the common iliac artery, bilateral stenosis of the internal carotid artery, left ventricular thrombus formation). Examples of additional findings are given in Figures 1–3.



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  		Figure 1a: Images obtained in 72-year-old woman who had severe left-sided claudication (Fontaine stage IIb). (a) Coronal oblique whole-body MR angiographic image obtained with 3D FLASH sequence (3.46/1.21; flip angle, 25°; bandwidth, 360 Hz/pixel) revealed high-grade stenoses (horizontal arrows) of the superficial femoral artery on both sides. Findings in the left leg were confirmed with DSA findings. An additional finding was an accessory renal artery (vertical arrow). (b) Transverse FLAIR images (8800/108; flip angle, 150°; bandwidth, 130 Hz/pixel). (c) Coronal (left) and sagittal (right) maximum intensity projections from transverse time-of-flight images (36/7.15; flip angle, 30°; bandwidth, 73 Hz/pixel) show that, despite discrete microangiopathic lesions (arrows), no disease was found. (d) Double oblique cardiac delayed-enhancement images (ejection fraction, 59%) obtained with inversion-recovery turbo FLASH sequence (11.04/4.4; flip angle, 30°; bandwidth, 140 Hz/pixel) show that no disease was evident.

 


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  		Figure 1b: Images obtained in 72-year-old woman who had severe left-sided claudication (Fontaine stage IIb). (a) Coronal oblique whole-body MR angiographic image obtained with 3D FLASH sequence (3.46/1.21; flip angle, 25°; bandwidth, 360 Hz/pixel) revealed high-grade stenoses (horizontal arrows) of the superficial femoral artery on both sides. Findings in the left leg were confirmed with DSA findings. An additional finding was an accessory renal artery (vertical arrow). (b) Transverse FLAIR images (8800/108; flip angle, 150°; bandwidth, 130 Hz/pixel). (c) Coronal (left) and sagittal (right) maximum intensity projections from transverse time-of-flight images (36/7.15; flip angle, 30°; bandwidth, 73 Hz/pixel) show that, despite discrete microangiopathic lesions (arrows), no disease was found. (d) Double oblique cardiac delayed-enhancement images (ejection fraction, 59%) obtained with inversion-recovery turbo FLASH sequence (11.04/4.4; flip angle, 30°; bandwidth, 140 Hz/pixel) show that no disease was evident.

 


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  		Figure 1c: Images obtained in 72-year-old woman who had severe left-sided claudication (Fontaine stage IIb). (a) Coronal oblique whole-body MR angiographic image obtained with 3D FLASH sequence (3.46/1.21; flip angle, 25°; bandwidth, 360 Hz/pixel) revealed high-grade stenoses (horizontal arrows) of the superficial femoral artery on both sides. Findings in the left leg were confirmed with DSA findings. An additional finding was an accessory renal artery (vertical arrow). (b) Transverse FLAIR images (8800/108; flip angle, 150°; bandwidth, 130 Hz/pixel). (c) Coronal (left) and sagittal (right) maximum intensity projections from transverse time-of-flight images (36/7.15; flip angle, 30°; bandwidth, 73 Hz/pixel) show that, despite discrete microangiopathic lesions (arrows), no disease was found. (d) Double oblique cardiac delayed-enhancement images (ejection fraction, 59%) obtained with inversion-recovery turbo FLASH sequence (11.04/4.4; flip angle, 30°; bandwidth, 140 Hz/pixel) show that no disease was evident.

 


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  		Figure 1d: Images obtained in 72-year-old woman who had severe left-sided claudication (Fontaine stage IIb). (a) Coronal oblique whole-body MR angiographic image obtained with 3D FLASH sequence (3.46/1.21; flip angle, 25°; bandwidth, 360 Hz/pixel) revealed high-grade stenoses (horizontal arrows) of the superficial femoral artery on both sides. Findings in the left leg were confirmed with DSA findings. An additional finding was an accessory renal artery (vertical arrow). (b) Transverse FLAIR images (8800/108; flip angle, 150°; bandwidth, 130 Hz/pixel). (c) Coronal (left) and sagittal (right) maximum intensity projections from transverse time-of-flight images (36/7.15; flip angle, 30°; bandwidth, 73 Hz/pixel) show that, despite discrete microangiopathic lesions (arrows), no disease was found. (d) Double oblique cardiac delayed-enhancement images (ejection fraction, 59%) obtained with inversion-recovery turbo FLASH sequence (11.04/4.4; flip angle, 30°; bandwidth, 140 Hz/pixel) show that no disease was evident.

 


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  		Figure 2a: MR images in 61-year-old man suspected of having iliac aneurysm. (a) Coronal oblique 3D FLASH study (3.46/1.21, 25° flip angle) shows iliac aneurysm (thick arrow) and substantial atherosclerotic disease (thin arrow), which were confirmed at DSA. MR also demonstrated occlusion of right internal carotid (arrowhead). (b) Transverse FLAIR images (8800/108, 150° flip angle) show large prior cerebral infarction (arrows) in right occipital lobe. (c) Coronal (left) and slightly oblique-transverse coronal (right) maximum intensity projections from transverse time-of-flight MR (36/7.15, 30° flip angle) show occluded right internal carotid (arrows). (d) Double-oblique cardiac delayed-enhancement inversion-recovery turbo FLASH images (11.04/4.4, 30° flip angle) show prior transmural myocardial infarction (arrowheads) in area supplied by right coronary artery (37% ejection fraction).

 


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  		Figure 2b: MR images in 61-year-old man suspected of having iliac aneurysm. (a) Coronal oblique 3D FLASH study (3.46/1.21, 25° flip angle) shows iliac aneurysm (thick arrow) and substantial atherosclerotic disease (thin arrow), which were confirmed at DSA. MR also demonstrated occlusion of right internal carotid (arrowhead). (b) Transverse FLAIR images (8800/108, 150° flip angle) show large prior cerebral infarction (arrows) in right occipital lobe. (c) Coronal (left) and slightly oblique-transverse coronal (right) maximum intensity projections from transverse time-of-flight MR (36/7.15, 30° flip angle) show occluded right internal carotid (arrows). (d) Double-oblique cardiac delayed-enhancement inversion-recovery turbo FLASH images (11.04/4.4, 30° flip angle) show prior transmural myocardial infarction (arrowheads) in area supplied by right coronary artery (37% ejection fraction).

 


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  		Figure 2c: MR images in 61-year-old man suspected of having iliac aneurysm. (a) Coronal oblique 3D FLASH study (3.46/1.21, 25° flip angle) shows iliac aneurysm (thick arrow) and substantial atherosclerotic disease (thin arrow), which were confirmed at DSA. MR also demonstrated occlusion of right internal carotid (arrowhead). (b) Transverse FLAIR images (8800/108, 150° flip angle) show large prior cerebral infarction (arrows) in right occipital lobe. (c) Coronal (left) and slightly oblique-transverse coronal (right) maximum intensity projections from transverse time-of-flight MR (36/7.15, 30° flip angle) show occluded right internal carotid (arrows). (d) Double-oblique cardiac delayed-enhancement inversion-recovery turbo FLASH images (11.04/4.4, 30° flip angle) show prior transmural myocardial infarction (arrowheads) in area supplied by right coronary artery (37% ejection fraction).

 


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  		Figure 2d: MR images in 61-year-old man suspected of having iliac aneurysm. (a) Coronal oblique 3D FLASH study (3.46/1.21, 25° flip angle) shows iliac aneurysm (thick arrow) and substantial atherosclerotic disease (thin arrow), which were confirmed at DSA. MR also demonstrated occlusion of right internal carotid (arrowhead). (b) Transverse FLAIR images (8800/108, 150° flip angle) show large prior cerebral infarction (arrows) in right occipital lobe. (c) Coronal (left) and slightly oblique-transverse coronal (right) maximum intensity projections from transverse time-of-flight MR (36/7.15, 30° flip angle) show occluded right internal carotid (arrows). (d) Double-oblique cardiac delayed-enhancement inversion-recovery turbo FLASH images (11.04/4.4, 30° flip angle) show prior transmural myocardial infarction (arrowheads) in area supplied by right coronary artery (37% ejection fraction).

 


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  		Figure 3a: Severe claudication of the left leg (Fontaine stage IIb) in 63-year-old man. (a) Coronal oblique whole-body 3D FLASH MR angiogram demonstrates occlusion (arrow) of left superficial femoral artery. Findings in the left leg were confirmed with DSA findings. Additional findings were minor atherosclerotic changes in the internal carotid artery on the right (arrowhead). (b) Transverse FLAIR image shows microangiopathic lesions (arrows). (c) Coronal maximum intensity projection from transverse time-of-flight image depicts normal intracranial vessels. (d) Short-axis true fast imaging with steady-state precession images show hypokinetic regions (arrows) (ejection fraction, 57%), which could be observed in the anteroseptal regions of the left ventricle. (e) Double oblique inversion-recovery turbo FLASH images show no delayed enhancement.

 


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  		Figure 3b: Severe claudication of the left leg (Fontaine stage IIb) in 63-year-old man. (a) Coronal oblique whole-body 3D FLASH MR angiogram demonstrates occlusion (arrow) of left superficial femoral artery. Findings in the left leg were confirmed with DSA findings. Additional findings were minor atherosclerotic changes in the internal carotid artery on the right (arrowhead). (b) Transverse FLAIR image shows microangiopathic lesions (arrows). (c) Coronal maximum intensity projection from transverse time-of-flight image depicts normal intracranial vessels. (d) Short-axis true fast imaging with steady-state precession images show hypokinetic regions (arrows) (ejection fraction, 57%), which could be observed in the anteroseptal regions of the left ventricle. (e) Double oblique inversion-recovery turbo FLASH images show no delayed enhancement.

 


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  		Figure 3c: Severe claudication of the left leg (Fontaine stage IIb) in 63-year-old man. (a) Coronal oblique whole-body 3D FLASH MR angiogram demonstrates occlusion (arrow) of left superficial femoral artery. Findings in the left leg were confirmed with DSA findings. Additional findings were minor atherosclerotic changes in the internal carotid artery on the right (arrowhead). (b) Transverse FLAIR image shows microangiopathic lesions (arrows). (c) Coronal maximum intensity projection from transverse time-of-flight image depicts normal intracranial vessels. (d) Short-axis true fast imaging with steady-state precession images show hypokinetic regions (arrows) (ejection fraction, 57%), which could be observed in the anteroseptal regions of the left ventricle. (e) Double oblique inversion-recovery turbo FLASH images show no delayed enhancement.

 


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  		Figure 3d: Severe claudication of the left leg (Fontaine stage IIb) in 63-year-old man. (a) Coronal oblique whole-body 3D FLASH MR angiogram demonstrates occlusion (arrow) of left superficial femoral artery. Findings in the left leg were confirmed with DSA findings. Additional findings were minor atherosclerotic changes in the internal carotid artery on the right (arrowhead). (b) Transverse FLAIR image shows microangiopathic lesions (arrows). (c) Coronal maximum intensity projection from transverse time-of-flight image depicts normal intracranial vessels. (d) Short-axis true fast imaging with steady-state precession images show hypokinetic regions (arrows) (ejection fraction, 57%), which could be observed in the anteroseptal regions of the left ventricle. (e) Double oblique inversion-recovery turbo FLASH images show no delayed enhancement.

 


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  		Figure 3e: Severe claudication of the left leg (Fontaine stage IIb) in 63-year-old man. (a) Coronal oblique whole-body 3D FLASH MR angiogram demonstrates occlusion (arrow) of left superficial femoral artery. Findings in the left leg were confirmed with DSA findings. Additional findings were minor atherosclerotic changes in the internal carotid artery on the right (arrowhead). (b) Transverse FLAIR image shows microangiopathic lesions (arrows). (c) Coronal maximum intensity projection from transverse time-of-flight image depicts normal intracranial vessels. (d) Short-axis true fast imaging with steady-state precession images show hypokinetic regions (arrows) (ejection fraction, 57%), which could be observed in the anteroseptal regions of the left ventricle. (e) Double oblique inversion-recovery turbo FLASH images show no delayed enhancement.

 

   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
References
 
In our study, we found good to excellent image quality in all patient examinations. Venous superimposition was evident in very few patients, and it seriously hampered assessment of arterial vessels in only one patient. The sensitivity and specificity values of conventional DSA were comparable to values for single-station MR angiography that were described in the literature (20–23). Furthermore, MR imaging represents the standard of reference for cardiac functional assessment (24–26) and provides high diagnostic accuracy for the detection of prior cerebral ischemic episodes (16,27,28).

Concomitant Vascular Disease
Since PAOD, coronary artery disease, cerebrovascular disease, and atherosclerotic renal artery stenosis are all manifestations of atherosclerosis or atherothrombosis, it is therefore not surprising that the four conditions commonly occur together (29). Knowledge of the magnitude of coexisting atherosclerotic disease and its prognosis is essential for the physician treating the patient with PAOD so that the local disease can be treated in the systemic context. Although the location and extent of vessel lesions are important, relevant changes involve the target organs (ie, myocardium, brain, kidneys) as well. As a consequence, when the physician assesses the patient with atherosclerosis, a diagnostic technique should provide information about vessels and target organs.

The prevalence of coronary artery disease in patients with intermittent claudication is 40%–60%, although the patients may be asymptomatic, and increases with the severity of PAOD (5,30). The link between PAOD and cerebrovascular disease seems to be weaker, but again up to 60% of patients with claudication exhibit some evidence of cerebrovascular disease. Similarly, renal artery stenosis is common in patients who have cardiovascular disease, and especially in those with carotid artery stenosis and/or peripheral vascular disease (31). In the present study, 56% of patients with PAOD also showed evidence of cerebrovascular disease, whereas high-grade renal artery stenosis was diagnosed in 19% of patients. Although fewer patients were included in our study, prevalence of atherosclerotic manifestations in carotid and renal arteries is comparable to that in the previously mentioned studies. Because two false-negative results could occur in either the same patient or not, correlation of sensitivity values to just two values could be estimated. Therefore, the estimation with the generalized estimating equations seems to be an exercise in overfitting. Sensitivity and specificity values in different regions, however, seem to be weakly correlated.

Clinical Implications
Nesto et al (32) reported that 57% (17 of 30) of patients who have diabetes mellitus and peripheral artery disease but in whom clinical suspicion of coronary artery disease is lacking exhibited abnormalities at scintigraphy with thallium 201 (201Tl)-dipyridamole. Myocardial ischemia was diagnosed in 47% (14 of 30) of patients, whereas prior clinically silent myocardial infarction was evident in 37% (11 of 30) of patients. Similar results were reported by Darbar et al (30). They examined 84 consecutive patients who had PAOD but did not have symptoms of coronary artery disease by using imaging with 201Tl-dipyridamole and found abnormal perfusion patterns in 48 (57%) patients. After following up the patients for a mean of 66 months, Darbar et al (30) suggested that results of imaging with 201Tl-dipyridamole are valuable prognostic indicators for long-term event-free survival in this cohort of patients. Controversy exists about cardiac investigations, however, at imaging with 201Tl-dipyridamole in patients with peripheral vascular disease prior to surgery for abdominal aortic aneurysm. According to Galland (33), there is no evidence that identification and correction of coronary artery disease in asymptomatic patients results in either decreased surgical mortality or increased long-term survival. As a consequence, the routine use of imaging with 201Tl-dipyridamole cannot be justified. In contrast, researchers in several other studies concluded that a systematic vascular screening strategy that is based on noninvasive techniques can be useful in the detection of the presence of concomitant coronary artery disease (4) and carotid artery disease (4,34–37) in the patient who undergoes surgery for vascular disease.

Specifically, in one study, von Kemp et al (4) evaluated the vascular system of 200 patients by using different modalities. In this study, new atherosclerotic plaque formations were diagnosed in 64.5% (n = 129) of patients, which immediately affected the therapeutic strategy in 21% (n = 42) of the patients. In addition, the presence of coronary artery disease and of cardiac failure was one of the major determinants of short- and long-term prognosis (4). Furthermore, von Kemp et al (4) concluded that, in a substantial number of patients, newly diagnosed concomitant diseases in the patient who undergoes surgery for vascular disease contribute to alteration of surgical treatment and also have important implications for patient prognosis. We also diagnosed previously unknown disease in 84% of our patients; these findings are similar to those of von Kemp et al. Overall, these findings required midterm follow-up or therapy in 24 (75%) of 32 patients, whereas a change of therapy or immediate treatment was necessary in three (9%) patients.

Hughson et al (38) found that 6% of individuals with PAOD had a history of a previous stroke, compared with none in age- and sex-matched control subjects. In the Basle longitudinal study, 12% of male survivors of a cerebral ischemic event who had PAOD developed a stroke during 11 years of follow-up, compared with this finding in 4% of control subjects (39). Furthermore, Vernino et al (40) reported that 22% of patients died because of cardiac causes (myocardial infarction, congestive heart failure, fatal arrhythmias) after an initial cerebral infarction, whereas recurrent stroke accounted for 9% of deaths. Consequently, Vernino et al postulated that it would be worthwhile to determine if mortality after a stroke could be reduced by means of screening patients with cerebral infarction for occult ischemic heart disease. When one considers that patients who have experienced prior cerebral infarction have a significantly higher risk of further serious complications or cerebral reinfarction (40,41), exact staging of systemic atherosclerotic disease, as well as a history of cerebral infarction, seems to be crucial in terms of further treatment of and prognosis in these patients.

The latter point leads to an emphasis on the value of a technique that has the capability for noninvasive assessment of the vasculature of the whole body, as well as for assessment of cardiac function and prior tissue death in the brain and heart of patients who manifest regional atherosclerotic disease.

In the present study, patients with PAOD also exhibited systolic cardiac wall motion abnormalities (n = 21), delayed enhancement (n = 7), or evidence of prior cerebral infarction (n = 4).

Limitations
The examination protocol of the present study did not incorporate a myocardial perfusion examination that included evaluation at rest and at stress, which is the most sensitive MR imaging technique for the diagnosis of hemodynamic relevant coronary artery disease. This type of myocardial perfusion examination was not included because an additional contrast agent injection would be required. Perfusion examinations cannot be performed after MR angiography because of excessive contrast agent deposition in the patient. Conversely, performance of examinations at rest and at stress before MR angiography is possible; however, an application of contrast medium probably would cause a decrease in image quality in MR angiographic data sets. Moreover, injection of medication for induction of stress could cause premature termination of the examination as a result of side effects of the drug. Although results of perfusion examination at rest and at stress provide high-quality information about epicardial blood vessel status (42,43), indirect parameters such as regional cardiac wall motion and delayed enhancement also can provide accurate information about significant atherosclerotic involvement of coronary arteries (44–46).

Image reading was performed by one reader for the MR angiographic images and the DSA images. Readers, however, were experienced radiologists with more than 5 years of experience in cardiovascular MR imaging, as well as in diagnostic and interventional angiographic procedures.

The total imaging time was 29 minutes; however, in-room time amounted to about 50–55 minutes because of the prolonged image reconstruction times associated with MR angiographic sequences that employ parallel imaging. This problem should be resolved in the near future through the use of more powerful hardware and image reconstruction algorithms. Another reason for the discrepancy between imaging time and in-room time is that the acquisition of delayed-enhancement images requires a waiting period of 10 minutes after contrast material injection.

We conclude that whole-body MR imaging evaluation of patients who are suspected of having systemic atherosclerotic disease with an MR imaging system that has 32 receiver channels is feasible. With DSA as the reference standard, we found a sensitivity and specificity of whole-body MR angiography for the detection of significant atherosclerotic plaques of 96% for both values. Additional MR imaging findings necessitated midterm follow-up or therapy in 24 (75%) of 32 patients and a change of therapy or immediate treatment in three (9%) patients.


   ACKNOWLEDGMENTS
 
We thank Reinhard Vonthein, PhD, Department of Medical Biometry, University of Tuebingen, Tuebingen, Germany, for performing the statistical estimation of sensitivity and specificity for the detection of stenosis.


   FOOTNOTES
 

Abbreviations: DSA = digital subtraction angiography • FLAIR = fluid-attenuated inversion recovery • FLASH = fast low-angle shot • PAOD = peripheral arterial occlusive disease • 3D = three-dimensional

Authors stated no financial relationship to disclose.

Author contributions: Guarantors of integrity of entire study, M.F., A.M.S., C.D.C., S.M.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; approval of final version of submitted manuscript, all authors; literature research, M.F., N.I.S., U.K., T.N., S.M.; clinical studies, M.F., A.M.S., K.T., T.N., C.B., H.P.S., S.M.; statistical analysis, M.F., A.M.S., C.B., S.M.; and manuscript editing, all authors


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 DISCUSSION
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